If I<escape_function> is set then the format is processed by this
function before being returned.
+DEPRECATED? (mostly unused, expensive)
If I<format_function> is set then the detail is handed to this callback
for processing.
=cut
+#totally false laziness w/cust_bill_pkg->detail
sub formatted {
my ( $self, %opt ) = @_;
my $format = $opt{format} || '';